In addition of a previous post which explains how to add Exchange Online on the Exchange Management Console (http://blog.hametbenoit.info/2011/05/06/office-365-add-your-office-365-forest-on-your-exchange-management-console/) you can also do the same with PowerShell
To be able to use PowerShell to manage Exchange Online, follow steps provided here http://help.outlook.com/en-us/140/cc546278.aspx